Aptinyx (APTX) 10-K 21 Mar 19 2018 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Mar. 18, 2019	Jun. 29, 2018
Document and Entity Information
Entity Registrant Name	Aptinyx Inc.
Entity Central Index Key	0001674365
Document Type	10-K
Document Period End Date	Dec. 31, 2018
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Well-known Seasoned Issuer	No
Entity Filer Category	Non-accelerated Filer
Entity Public Float			$ 368.2
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		33,562,211
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	FY

Balance Sheets

Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 150,637	$ 92,136
Restricted cash	252
Accounts receivable	578	937
Prepaid expenses and other current assets	1,784	1,960
Total current assets	153,251	95,033
Other assets	673	473
Property and equipment, net	1,690	1,816
Total assets	155,614	97,322
Current liabilities:
Accounts payable	1,889	1,537
Accrued expenses and other current liabilities	3,996	2,835
Total current liabilities	5,885	4,372
Other long-term liabilities	418	282
Total liabilities	6,303	4,654
Commitments and contingencies
Stockholders' equity (deficit):
Preferred stock, $0.01 par value, 10,000 and no shares authorized as of December 31, 2018 and December 31, 2017, respectively; no shares issued and outstanding as of December 31, 2018 and December 31, 2017, respectively
Common stock, $0.01 par value, 150,000 shares authorized, 33,341 issued and outstanding as of December 31, 2018 and 900,000 shares authorized, 5,342 issued and outstanding as of December 31, 2017	333	53
Additional paid-in capital	254,516	12,486
Accumulated deficit	(105,538)	(52,257)
Total stockholders’ equity (deficit)	149,311	(39,718)
Total liabilities, convertible preferred stock and stockholders’ equity (deficit)	$ 155,614	97,322
Series A-1
Convertible preferred stock:
Convertible preferred stock		22,650
Series A-2
Convertible preferred stock:
Convertible preferred stock		39,979
Series B
Convertible preferred stock:
Convertible preferred stock		$ 69,757

Balance Sheets (Parenthetical)

Balance Sheets (Parenthetical) - $ / shares shares in Thousands	Dec. 31, 2018	Dec. 31, 2017
Convertible preferred stock, shares authorized		560,181
Convertible preferred stock, shares issued		560,181
Convertible preferred stock, shares outstanding		560,181
Preferred Stock, Par or Stated Value Per Share	$ 0.01	$ 0.01
Preferred Stock, Shares Authorized	10,000	0
Preferred Stock, Shares Issued	0	0
Preferred Stock, Shares Outstanding	0	0
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized	150,000	900,000
Common stock, shares issued	33,341	5,342
Common stock, shares outstanding	33,341	5,342
Series A-1
Convertible preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Convertible preferred stock, shares authorized	0	151,773
Convertible preferred stock, shares issued	0	151,773
Convertible preferred stock, shares outstanding	0	151,773
Series A-2
Convertible preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Convertible preferred stock, shares authorized	0	173,453
Convertible preferred stock, shares issued	0	173,453
Convertible preferred stock, shares outstanding	0	173,453
Series B
Convertible preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Convertible preferred stock, shares issued	0	234,955
Convertible preferred stock, shares outstanding	0	234,955

Statements of Operations and Co

Statements of Operations and Comprehensive Loss - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Statements of Operations and Comprehensive Loss
Collaboration and grant revenue	$ 6,574	$ 4,962
Type of revenue	aptx:CollaborationAndGrantMember	aptx:CollaborationAndGrantMember
Operating expenses:
Research and development	$ 48,788	$ 31,644
General and administrative	12,674	5,551
Total operating expenses	61,462	37,195
Loss from operations	(54,888)	(32,233)
Other income	1,607	165
Net loss and comprehensive loss	$ (53,281)	$ (32,068)
Net loss per share attributable to common stockholders, basic and diluted (in dollars per share)	$ (2.64)	$ (6.17)
Weighted-average number of common shares outstanding, basic and diluted (in shares)	20,199	5,196

Statements of Convertible Prefe

Statements of Convertible Preferred Stock - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Convertible Preferred Stock Rollforward
Convertible preferred stock shares beginning balance	560,181
Convertible preferred stock shares ending balance		560,181
Series A-1
Convertible Preferred Stock Rollforward
Convertible preferred stock beginning balance	$ 22,650	$ 22,650
Convertible preferred stock shares beginning balance	151,773	151,773
Conversion of preferred stock upon IPO	$ (22,650)
Conversion of preferred stock upon IPO (in shares)	(151,773)
Convertible preferred stock shares ending balance	0	151,773
Convertible preferred stock ending balance		$ 22,650
Series A-2
Convertible Preferred Stock Rollforward
Convertible preferred stock beginning balance	$ 39,979
Convertible preferred stock shares beginning balance	173,453
Issuance of convertible preferred stock, net of issuance costs		$ 39,979
Issuance of convertible preferred stock, net of issuance costs (in shares)		173,453
Conversion of preferred stock upon IPO	$ (39,979)
Conversion of preferred stock upon IPO (in shares)	(173,453)
Convertible preferred stock shares ending balance	0	173,453
Convertible preferred stock ending balance		$ 39,979
Series B
Convertible Preferred Stock Rollforward
Convertible preferred stock beginning balance	$ 69,757
Convertible preferred stock shares beginning balance	234,955
Issuance of convertible preferred stock, net of issuance costs		$ 69,757
Issuance of convertible preferred stock, net of issuance costs (in shares)		234,955
Conversion of preferred stock upon IPO	$ (69,757)
Conversion of preferred stock upon IPO (in shares)	(234,955)
Convertible preferred stock shares ending balance	0	234,955
Convertible preferred stock ending balance		$ 69,757

Statements of Convertible Pre_2

Statements of Convertible Preferred Stock (Parenthetical) $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)
Series A-2
Stock issuance costs capitalized	$ 21
Series B
Stock issuance costs capitalized	$ 243

Statements of Stockholders_ Equ

Statements of Stockholders’ Equity (Deficit) - USD ($) shares in Thousands, $ in Thousands	Common stock	Additional paid-in capital	Accumulated deficit	Total
Stockholders' (deficit) equity beginning balance at Dec. 31, 2016	$ 50	$ 11,588	$ (20,189)	$ (8,551)
Stockholders' (deficit) equity shares beginning balance at Dec. 31, 2016	5,049
Stockholders' (Deficit) Equity Rollforward
Issuance of common stock upon vesting of restricted stock awards	$ 3	(3)
Issuance of common stock upon vesting of restricted stock awards (in shares)	293
Stock-based compensation		901		901
Net loss			(32,068)	$ (32,068)
Stockholders' (deficit) equity shares ending balance at Dec. 31, 2017	5,342			5,342
Stockholders' (deficit) equity ending balance at Dec. 31, 2017	$ 53	12,486	(52,257)	$ (39,718)
Stockholders' (Deficit) Equity Rollforward
Issuance of common stock upon vesting of restricted stock awards	$ 3	(3)
Issuance of common stock upon vesting of restricted stock awards (in shares)	293
Stock-based compensation		3,318		3,318
Conversion of preferred stock upon IPO	$ 203	132,183		132,386
Conversion of preferred stock upon IPO (in shares)	20,306
Issuance of common stock upon IPO, net of underwriters' discount and other offering costs of $2,902	$ 74	106,431		106,505
Issuance of common stock upon IPO, net of underwriters' discount and other offering costs of $2,902 (in shares)	7,360
Issuance of common stock upon exercise of stock options		101		101
Issuance of common stock upon exercise of stock options (in shares)	40
Net loss			(53,281)	$ (53,281)
Stockholders' (deficit) equity shares ending balance at Dec. 31, 2018	33,341			33,341
Stockholders' (deficit) equity ending balance at Dec. 31, 2018	$ 333	$ 254,516	$ (105,538)	$ 149,311

Statements of Stockholders_ E_2

Statements of Stockholders’ Equity (Deficit) (Parenthetical) $ in Thousands	12 Months Ended
	Dec. 31, 2018USD ($)
Statements of stockholders’ (deficit) equity
Stock issuance costs capitalized	$ 3,012

Statements of Cash Flows

Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Cash flows from operating activities:
Net loss	$ (53,281)	$ (32,068)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization expense	457	405
Stock-based compensation expense	3,318	901
Changes in operating assets and liabilities:
Prepaid expenses and other assets	(260)	(1,355)
Accounts receivable	359	(448)
Accounts payable	418	(124)
Accrued expenses and other liabilities	1,541	(46)
Net cash used in operating activities	(47,448)	(32,735)
Cash flows from investing activities:
Purchases of property and equipment	(407)	(1,577)
Net cash used in investing activities	(407)	(1,577)
Cash flows from financing activities:
Payment of deferred issuance costs associated with Series B convertible preferred stock financing	(232)
Proceeds from stock options exercised	101
Proceeds from initial public offering, net of underwriters discounts	109,517
Payment of deferred offering costs	(3,012)
Net cash provided by financing activities	106,374	109,968
Net increase in cash, cash equivalents and restricted cash	58,519	75,656
Cash, cash equivalents and restricted cash, at beginning of period	92,609	16,953
Cash, cash equivalents and restricted cash, at end of period	$ 151,128	92,609
Supplemental disclosure of non-cash investing and financing activities:
Series B convertible preferred stock financing costs not yet paid		232
Series A-2
Cash flows from financing activities:
Proceeds from issuance of convertible preferred stock, net issuance of costs		39,979
Series B
Cash flows from financing activities:
Proceeds from issuance of convertible preferred stock, net issuance of costs		$ 69,989

Organization

Organization	12 Months Ended
	Dec. 31, 2018
Organization
Organization	1. Organization Description of business Aptinyx Inc. (the “Company” or “Aptinyx”) was incorporated in Delaware on June 24, 2015 and maintains its headquarters in Evanston, Illinois. Aptinyx is a clinical‑stage biopharmaceutical company focused on the discovery, development, and commercialization of novel, proprietary, synthetic small molecules for the treatment of brain and nervous system disorders. Aptinyx has a platform for discovering proprietary compounds that work through a novel mechanism: modulation of N‑methyl‑D‑aspartate receptors (“NMDAr”), which are vital to normal and effective brain and nervous system functions. This mechanism has applicability across a number of brain and nervous system disorders. Liquidity and capital resources The Company has incurred losses and negative cash flows from operations since inception and had an accumulated deficit of $105.5 million as of December 31, 2018. The Company expects to incur substantial operating losses for the next several years and will need to obtain additional financing in order to complete clinical studies and launch and commercialize any product candidates for which it receives regulatory approval. There can be no assurance that such financing will be available or will be at terms acceptable to the Company. As of December 31, 2018, the Company had cash and cash equivalents of $150.6 million which it believes will be sufficient to fund its planned operations for a period of at least twelve months from the date of the issuance of these financial statements. Initial public offering On June 20, 2018, the Company’s registration statement on Form S - 1 (File No. 333‑225150) relating to the initial public offering (“IPO”) of its common stock became effective and on June 25, 2018, the IPO closed. Pursuant to the IPO, the Company issued and sold 7,359,998 shares of common stock at a public offering price of $16.00 per share, which included 959,999 shares sold pursuant to the exercise of the underwriters’ option to purchase additional shares. The Company received net proceeds of $106.5 million after deducting underwriting discounts and commissions and other offering costs of $3.0 million. The shares began trading on the Nasdaq Global Select Market on June 21, 2018. Upon the closing of the IPO, all of the Company’s outstanding shares of convertible preferred stock automatically converted into 20,306,497 shares of common stock at the applicable conversion ratio. On June 7, 2018, the Company effected a one-for-27.58621 reverse stock split of its issued and outstanding shares of common stock and a proportional adjustment to the existing conversion ratios for each series of the Company's redeemable convertible preferred stock (see Note 10). Accordingly, all share and per share amounts for all periods presented in the financial statements have been adjusted retroactively, where applicable, to reflect this reverse stock split and adjustment of the preferred stock conversion ratios. The Company is also authorized to issue 10 million shares of undesignated preferred stock, par value $0.01, in one or more series. As of December 31, 2018, no shares of preferred stock were issued or outstanding.

Basis of presentation

Basis of presentation	12 Months Ended
	Dec. 31, 2018
Basis of presentation
Basis of Presentation	2. Basis of presentation The accompanying financial statements are prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”). From time to time, new accounting pronouncements are issued by the Financial Accounting Standards Board (“FASB”), or other standard setting bodies and adopted by the Company as of the specified effective date. Unless otherwise discussed, the impact of recently issued standards that are not yet effective will not have a material impact on the Company’s financial statements upon adoption. Under the Jumpstart Our Business Startups Act of 2012, as amended (“the JOBS Act”), the Company meets the definition of an emerging growth company, and has elected the extended transition period for complying with new or revised accounting standards, which delays the adoption of these accounting standards until they would apply to private companies. Recently issued accounting pronouncements In February 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2016‑02, Leases (Topic 842) (“ASC 842”), which requires a lessee to recognize assets and liabilities on the balance sheet for operating leases and changes many key definitions, including the definition of a lease. The new standard includes a short‑term lease exception for leases with a term of 12 months or less, as part of which a lessee can make an accounting policy election not to recognize lease assets and lease liabilities. Lessees will continue to differentiate between finance leases (previously referred to as capital leases) and operating leases using classification criteria that are substantially similar to the previous guidance. In July 2018, the FASB issued ASU No. 2018-11, Leases (Topic 842): Targeted Improvements (“ASU 2018-11”), which offers a transition option to entities adopting ASC 842. Under ASU 2018-11, entities can elect to apply ASC 842 using a modified-retrospective adoption approach resulting in a cumulative effect adjustment to accumulated deficit at the beginning of the year in which the new lease standard is adopted, rather than adjustments to the earliest comparative period presented in their financial statements. The new standard will be effective for the Company beginning after December 15, 2019, and early adoption is permitted. The Company is currently evaluating the potential impact ASC 842 may have on its financial statements. In May 2014, the FASB issued ASU No. 2014‑09, Revenue from Contracts with Customers (“ASU 2014‑09”), which supersedes nearly all existing revenue recognition guidance. The core principle of ASU 2014‑09 is to recognize revenues when promised goods or services are transferred to customers in an amount that reflects the consideration to which an entity expects to be entitled for those goods or services. ASU 2014‑09 defines a five-step process to achieve this core principle and, in doing so, more judgment and estimates may be required within the revenue recognition process than are required under existing GAAP. The standard is effective for annual periods, including interim periods within those fiscal years, beginning after December 15, 2018, using either of the following transition methods: (i) a full retrospective approach reflecting the application of the standard in each prior reporting period with the option to elect certain practical expedients, or (ii) a retrospective approach with the cumulative effect of initially adopting ASU 2014‑09 recognized at the date of adoption (which includes additional footnote disclosures). The Company will adopt ASC 606 effective January 1, 2019 using the modified retrospective method which requires that any cumulative effect of initially applying ASC 606 be recognized as an adjustment to the opening balance of accumulated deficit on the date of adoption. The Company has concluded that the Research Collaboration Agreement with Allergan (see Note 4) was the only material contract still in process as of the adoption date. The Company has identified that the contract includes the following promised goods and/or services: (i) access to research licenses, (ii) performing research and development activities, and (iii) participating in a joint steering committee. The Company has concluded that, individually, these promised goods and/or services are not distinct, and therefore represent a single combined performance obligation that will be satisfied over-time. The Company is substantially complete with its assessment, and does not expect the adoption of ASC 606 to have a material impact on its financial position, results of operations or cash flows. Upon adoption, the Company expects to disaggregate revenue from the Research Collaboration Agreement from income earned under government grants which the Company has concluded fall outside of the scope of ASC 606.

Summary of significant accounti

Summary of significant accounting policies	12 Months Ended
	Dec. 31, 2018
Summary of significant accounting policies
Summary of significant accounting policies	3. Summary of significant accounting policies Use of estimates The financial statements are prepared in conformity with GAAP. This process requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities as of the date of the financial statements and the reported amounts of expenses during the reporting period. Actual results could differ from those estimates. Risk and uncertainties The Company’s future results of operations involve a number of risks and uncertainties. Factors that could affect the Company’s future operating results and cause actual results to vary materially from expectations include, but are not limited to, uncertainty of: future clinical study results, the scope, rate of progress and expense of the Company’s ongoing as well as any additional preclinical studies, clinical studies and other research and development activities, clinical study enrollment rate or design, the manufacturing of the Company’s product candidates, significant and changing government regulation, and the timing and receipt of any regulatory approvals. The Company’s product candidates require approvals from the U.S. Food and Drug Administration and comparable foreign regulatory agencies prior to commercial sales in their respective jurisdictions. There can be no assurance that any product candidates will receive the necessary approvals. If the Company was denied approval, approval was delayed or the Company was unable to maintain approval for any product candidate, it could have a materially adverse impact on the Company. The Company is dependent upon third‑party manufacturers to supply product for research and development activities in its programs. In particular, the Company relies and expects to continue to rely on a small number of manufacturers to supply it with its requirements for the active pharmaceutical ingredients and final drug product related to these programs. These programs could be adversely affected by a significant interruption in the supply of active pharmaceutical ingredients and final drug product. Revenue recognition Revenue is recognized when all terms and conditions of the agreements have been met, including that persuasive evidence of an arrangement exists, delivery has occurred or services have been rendered, the price is fixed or determinable and collectability is reasonably assured. The Company is reimbursed for certain costs incurred on specified research projects under the terms and conditions of a Research Collaboration Agreement that are reported within collaboration and grant revenue (as discussed in Note 4) in the statements of operations and comprehensive loss. The amounts of the reimbursements are recorded as revenues on a gross basis in accordance with ASC 605‑45— Revenue Recognition—Principal Agent Consideration . The core principle is that the entity should recognize revenue to depict the transfer of goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. ASC 605‑45 specifies various indicators that support the reporting of revenue on a gross basis. As the Company is considered the primary obligor, is exposed to credit risk, and has discretion in changing and selecting the supplier, the Company recognizes these reimbursements on a gross basis. The related expenses are primarily recorded within research and development expenses in the statements of operations and comprehensive loss. The Company is also reimbursed for certain costs associated with government grants that provide funding for certain types of expenditures in connection with research and development activities over a contractually‑defined period. Revenue related to government grants is recognized in the period during which the related costs are incurred and the related services are rendered, provided that the applicable performance obligations under the government grants have been met. The revenue is reported on a gross basis within collaboration and grant revenue and the related expenses are recorded within both general and administrative expenses and research and development expenses in the statements of operations and comprehensive loss. Accounts receivable Accounts receivable that management has the intent and ability to collect are reported in the balance sheets at outstanding amounts, less an allowance for doubtful accounts. During the years ended December 31, 2018 and 2017, one research collaborator, Allergan plc (“Allergan”) represented 75% and 80%, respectively, of the Company’s revenues (see Note 4). The associated accounts receivable were approximately $0.6 million and $0.6 million at December 31, 2018 and 2017, respectively. The remaining accounts receivable as of December 31, 2017 relate to the Company’s grants with the U.S. government. The Company writes off uncollectible receivables based on specific identification when the likelihood of collection is remote. No allowance was deemed necessary at December 31, 2018 and 2017. Cash, cash equivalents and restricted cash Cash and cash equivalents consist of cash and, if applicable, highly liquid investments with an original maturity of three months or less when purchased. The following table provides a reconciliation of cash, cash equivalents, and restricted cash reported within the balance sheets that sum to the total of the same such amounts shown in the statements of cash flows (amounts in thousands). As of December 31, Cash and cash equivalents $ 150,637 $ 92,136 Short-term and long-term restricted cash 491 473 Total cash, cash equivalents, and restricted cash shown in the statements of cash flows $ 151,128 $ 92,609 Amounts included in restricted cash represent those amounts required to be held as a security deposit in the form of letters of credit for the Company’s leased office facility and cash collateral held by credit card. Concentrations of credit risk The Company, at times, maintains cash and cash equivalents in accounts with a financial institution in excess of the amount insured by the Federal Deposit Insurance Corporation. The Company monitors the financial stability of this institution regularly and management does not believe there is significant credit risk associated with deposits in excess of federally insured amounts. Fair value of financial instruments ASC 820, Fair Value Measurement (“ASC 820”), establishes a fair value hierarchy for instruments measured at fair value that distinguishes between assumptions based on market data (observable inputs) and the Company’s own assumptions (unobservable inputs). Observable inputs are inputs that market participants would use in pricing the asset or liability based on market data obtained from sources independent of the Company. Unobservable inputs are inputs that reflect the Company’s assumptions about the inputs that market participants would use in pricing the asset or liability, and are developed based on the best information available in the circumstances. ASC 820 identifies fair value as the exchange price, or exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. As a basis for considering market participant assumptions in fair value measurements, ASC 820 establishes a three‑tier fair value hierarchy that distinguishes between the following: · Level 1 inputs are quoted prices (unadjusted) in active markets for identical assets or liabilities; · Level 2 inputs are inputs other than quoted prices included within Level 1 that are observable for the asset or liability, either directly or indirectly; and · Level 3 inputs are unobservable inputs that reflect the Company’s own assumptions about the assumptions market participants would use in pricing the asset or liability. Financial assets and liabilities are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. To the extent that the valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for instruments categorized in Level 3. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement. There were no Level 3 assets or liabilities as of December 31, 2018 or 2017. The carrying values reported in the Company’s balance sheets for cash and cash equivalents, restricted cash, accounts receivable, accounts payable, and accrued expenses are reasonable estimates of their fair values due to the short‑term nature of these items. Property and equipment Property and equipment are stated at cost. Maintenance and repairs are charged to expense as incurred. Additions, improvements and replacements are capitalized. Depreciation of property and equipment is provided for by the straight‑line method over the estimated useful lives of the related assets. The estimated useful lives of property and equipment are as follows: Description Estimated useful life Computer software and equipment 3 years Office equipment and furniture 5 years Laboratory equipment 5 years Leasehold improvements Lesser of the estimated useful life or term of the lease Impairment of long‑lived assets Long‑lived assets consist of property and equipment. Long‑lived assets to be held and used are tested for recoverability whenever events or changes in business circumstances indicate that the carrying amount of the assets may not be fully recoverable. If the sum of the estimated future undiscounted cash flows expected to result from the use and eventual disposition of an asset is less than the carrying amount of the asset group, an impairment loss is recognized. Measurement of an impairment loss is based on the fair value of the asset group. The Company has not recorded any impairment losses on long‑lived assets for the years ended December 31, 2018 and 2017. Research and development Research and development expenses are comprised of costs incurred in performing research and development activities, including salaries and benefits, facilities costs, overhead costs, depreciation, contract services and other related costs. Research and development costs are expensed to operations as the related obligation is incurred. The Company has entered into various research and development contracts with research institutions, clinical research organizations, clinical manufacturing organizations and other companies. These agreements are generally cancelable, and related payments are recorded as research and development expenses as incurred. Payments for these activities are based on the terms of the individual agreements, which may differ from the pattern of costs incurred, and are reflected on the balance sheet as prepaid or accrued expenses. The Company records accruals for estimated ongoing research costs. When evaluating the adequacy of the accrued liabilities, the Company analyzes progress of the studies, including the phase or completion of events, invoices received and contracted costs. Significant judgments and estimates may be made in determining the accrued balances at the end of any reporting period. Actual results could differ from the Company’s estimates. The Company’s historical accrual estimates have not been materially different from the actual costs. Convertible preferred stock The Company has applied the guidance in ASC 480‑10‑S99‑3A, SEC Staff Announcement: Classification and Measurement of Redeemable Securities and has therefore classified the Series A‑1, Series A‑2 and Series B convertible preferred stock (Note 10) as mezzanine equity. The convertible preferred stock is recorded outside of stockholders’ deficit because, in the event of certain deemed liquidation events considered not solely within the Company’s control, such as a merger, acquisition and sale of all or substantially all of the Company’s assets, the convertible preferred stock will become redeemable at the option of the holders. In the event of a change of control of the Company, proceeds received from the sale of such shares will be distributed in accordance with the liquidation preferences set forth in the Company’s Amended and Restated Certificate of Incorporation. The Company has determined not to adjust the carrying values of the convertible preferred stock to the liquidation preferences of such shares because of the uncertainty of whether or when such an event would occur. As described in Note 1, all previously outstanding convertible preferred stock was converted to common stock upon the completion of the Company’s IPO in June 2018. Stock‑based compensation The Company has stock‑based compensation plans that cover the Company’s directors and employees and are more fully described in Note 11. Stock‑based compensation cost is estimated at the grant date based on the fair value of the award, and the cost is recognized as expense ratably over the vesting period. Income taxes The Company accounts for income taxes under the liability method in accordance with FASB ASC 740, Income Taxes. Under this method, deferred income tax assets and liabilities are determined based on differences between financial reporting and tax bases of assets and liabilities and are measured using the enacted tax rates and laws that will be in effect when the differences are expected to reverse. A valuation allowance is established if it is more likely than not that all, or some portion, of deferred income tax assets will not be realized. The Company has recorded a full valuation allowance to reduce its net deferred income tax assets to zero. In the event the Company were to determine that it would be able to realize some or all its deferred income tax assets in the future, an adjustment to the deferred income tax asset valuation allowance would increase income in the period such determination was made. The Company recognizes the effect of income tax positions only if those positions are more likely than not of being sustained upon an examination. Any recognized income tax positions would be measured at the largest amount that is greater than 50% likely of being realized. Changes in recognition or measurement would be reflected in the period in which the change in judgment occurs. At December 31, 2018 and 2017, the Company had no liability for income tax associated with uncertain tax positions. The Company would recognize any corresponding interest and penalties associated with its income tax positions in income tax expense. There was no income tax interest or penalties incurred in 2018 or 2017. Segment data The Company manages its operations as a single segment for the purposes of assessing performance and making operating decisions. The Company’s singular focus is on advancing therapies to treat disorders of the brain and nervous system. All tangible assets are held in the United States and all revenue is generated in the United States. Comprehensive loss Comprehensive loss is equal to net loss as presented in the accompanying statements of operations and comprehensive loss. Net loss per share Basic net loss per share is calculated by dividing the net loss by the weighted‑average number of shares of common stock outstanding during the period, without consideration for common stock equivalents. Diluted net loss per share is the same as basic net loss per share, since the effects of potentially dilutive securities are antidilutive given the Company has reported net losses for each period presented.

Research collaboration agreemen

Research collaboration agreement with Allergan	12 Months Ended
	Dec. 31, 2018
Research collaboration and development services agreements with Allergan
Research collaboration and development services agreements with Allergan	4. Research collaboration agreement with Allergan On July 24, 2015, the Company entered into a Research Collaboration Agreement (“RCA”) with Naurex Inc., a subsidiary of Allergan plc (“Allergan”), focused on the research and discovery of small molecules that modulate NMDArs. The collaboration is supervised by a Joint Steering Committee (“JSC”) comprised of an equal number of representatives from both the Company and Allergan. Under the terms of the agreement, Allergan will pay the Company $1.0 million for each option exercised by Allergan. Under the terms of the agreement, the RCA will terminate upon the earlier of a predetermined anniversary of the RCA or on the date on which Allergan exercises three options to acquire molecules from a pool of eligible compounds. On May 16, 2018, Allergan exercised its option to acquire exclusive rights to develop and commercialize AGN-241751 within a predefined set of indications. During the year ended December 31, 2018, the Company recognized the $1.0 million non-refundable milestone payment within collaboration and grant revenue in the statements of operations and comprehensive loss as there were no remaining performance obligations associated with the optioned compound. Costs between the Company and Allergan with respect to each party’s share of development costs that have been incurred pursuant to the RCA are substantially recorded within research and development in the accompanying statements of operations and comprehensive loss. Reimbursable expenses under the RCA include chemistry, discovery, screening, and profiling efforts around novel NMDAr modulators from the Company’s discovery platform as well as salary of full-time employees at a fixed annual rate for each individual assigned to those efforts, consistent with oversight and guidance of the JSC. Such costs for each compound are considered reimbursable up until the point that the compound is selected by one of the collaboration parties. None of the costs reimbursed by Allergan in any period presented were directly related to the Company’s lead product candidates, NYX-2925, NYX-783, and NYX-458, which the Company selected under the collaboration. During each of the years ended December 31, 2018 and 2017, the Company recorded expenses of $7.9 million for certain development activities in accordance with the terms of the RCA of which 50% was reimbursed by Allergan. The Company received reimbursements of $3.9 million during each of the years ended December 31, 2018 and 2017, which were reported within collaboration and grant revenue in the statements of operations and comprehensive loss.

Prepaid expenses and other curr

Prepaid expenses and other current assets	12 Months Ended
	Dec. 31, 2018
Prepaid expenses and other current assets
Prepaid expenses and other current assets	6. Prepaid expenses and other current assets Prepaid expenses and other current assets consist of the following (in thousands): As of December 31, Prepaid clinical $ 728 $ 1,718 Prepaid insurance 673 137 Other prepaid expenses and current assets 383 105 Total prepaid expenses and other current assets $ 1,784 $ 1,960

Property and equipment

Property and equipment	12 Months Ended
	Dec. 31, 2018
Property and equipment
Property and equipment	7 . Property and equipment Property and equipment are as follows (in thousands): As of December 31, Computer software and equipment $ 15 $ 15 Office equipment and furniture 176 92 Laboratory equipment 1,571 1,529 Leasehold improvements 1,051 748 Construction in progress — 22 Less accumulated depreciation (1,123) (590) Property and equipment, net $ 1,690 $ 1,816 Depreciation expense was $0.5 million and $0.4 million for the years ended December 31, 2018 and 2017, respectively.

Accrued expenses and other curr

Accrued expenses and other current liabilities	12 Months Ended
	Dec. 31, 2018
Accrued expenses and other current liabilities
Accrued expenses and other current liabilities	8. Accrued expenses and other current liabilities Accrued expenses and other current liabilities consist of the following (in thousands): As of December 31, Employee-related expenses $ 2,043 $ 1,435 Development costs and sponsored research 915 737 Clinical trials 607 69 Other 431 594 Total accrued expenses and other current liabilities $ 3,996 $ 2,835

Operating leases

Operating leases	12 Months Ended
	Dec. 31, 2018
Operating leases
Operating leases	9. Operating leases The Company enters into various non‑cancelable, operating lease agreements for its facilities and equipment in order to conduct its operations. The Company expenses rent on a straight‑line basis over the life of the lease and has recorded deferred rent on the balance sheets within both accrued expenses and other current liabilities and other long-term liabilities. On October 13, 2016, the Company entered into a lease agreement with the landlord for office space totaling approximately 16,500 square feet. The term of this lease commenced on April 1, 2017 and continues through August 31, 2022. The Company has an option to renew the lease for one renewal term of 5 years. The lease provided the Company with a tenant improvement allowance of $0.4 million. The Company recorded the tenant improvement allowance incurred as a deferred lease incentive and is amortizing the deferred lease incentive through a reduction of rent expense ratably over the lease term. The Company provided the landlord with a security deposit in the form of a letter of credit in the amount of $0.4 million which is recorded within both restricted cash and other assets in the Company’s balance sheets as of December 31, 2018 and 2017. On July 18, 2018, the Company entered into a sublease agreement for additional office space adjacent to the Company’s existing headquarters in Evanston, Illinois, totaling approximately 6,172 square feet. The term of the lease commenced on July 18, 2018 and continues through September 30, 2022. On January 31, 2019, the sublease agreement was terminated, and the Company entered into an amended lease agreement with the landlord for the same additional office space. The terms commence on February 1, 2019 and continue through August 31, 2022. The total estimated base rent payments over the term of the amended sublease approximate $0.8 million. Total rent expense, inclusive of lease incentives, under the operating lease agreements amounted to $0.7 million and $0.6 million for the years ended December 31, 2018 and 2017, respectively. Aggregate future minimum annual rental commitments under these non‑cancelable lease agreements are as follows at December 31, 2018 (in thousands): Year ending December 31, 2019 $ 848 2020 860 2021 871 2022 587 2023 — Thereafter — $ 3,166

Convertible preferred stock, tr

Convertible preferred stock, tranche liability and stockholders’ equity (deficit)	12 Months Ended
	Dec. 31, 2018
Convertible preferred stock, tranche liability and stockholders’ deficit
Convertible preferred stock, tranche liability and stockholders’ deficit	10. Convertible preferred stock, tranche liability and stockholders’ equity (deficit) As described in Note 1, all previously outstanding convertible preferred stock was converted to common stock upon the completion of the Company’s IPO in June 2018. At December 31, 2017, convertible preferred stock consisted of the following (in thousands, except per share amounts): Shares Issuance Shares issued and price per Carrying Liquidation authorized outstanding share value preference Series A‑1 151,773 151,773 0.16472 $ 22,650 $ 25,000 Series A‑2 173,453 173,453 0.23061 39,979 40,000 Series B 234,955 234,955 0.29793 69,757 70,000 Total 560,181 560,181 $ 132,386 $ 135,000 Series A preferred stock On May 4, 2016, the Company entered into a purchase agreement (the “Series A Purchase Agreement”) for a private placement of up to 151,772,701 shares of Series A‑1 Convertible Preferred Stock (the “Series A‑1 Preferred Stock”) and 173,453,018 shares of Series A‑2 Convertible Preferred Stock (the “Series A‑2 Preferred Stock” and together with the Series A‑1 Preferred Stock, the “Series A Preferred Stock”) under the Series A Purchase Agreement. Of the 325,225,719 authorized shares of Series A Preferred Stock, 151,772,701 shares were designated Series A‑1 Preferred Stock at $0.16472 per share and 173,453,018 shares were designated Series A‑2 Preferred Stock at $0.23061 per share. The Series A Purchase Agreement obligated the investors to purchase, at the election of the Company’s board of directors (the “Board of Directors”), the Series A‑2 Preferred Stock at $0.23061 per share upon achieving certain clinical milestones. The determination as to whether the milestone event was met was subject to the certification by (i) the Board of Directors and (ii) the holders of at least a majority of the then‑outstanding Series A Preferred Stock. The Series A Purchase Agreement also obligated the Company to sell to each investor that elects to purchase such investor’s portion of Series A‑2 Preferred Stock at any time such number of shares of Series A‑2 Preferred Stock pro rata in accordance with the number of Series A‑1 Preferred Stock purchased at the initial closing (the “Tranche Rights”). In January 2017, the Company achieved its clinical milestone obligating the Company to sell its Series A‑2 Preferred Stock at $0.23061 per share. The milestone closing occurred on February 2, 2017. As of December 31, 2017, 151,772,701 shares of the Series A‑1 Preferred Stock and 173,453,018 shares of the Series A‑2 Preferred Stock were issued and outstanding. These shares were issued in exchange for cash proceeds of $64.7 million, net of issuance costs. Series B preferred stock On December 11, 2017, the Company entered into a purchase agreement (the “Series B Purchase Agreement”) for a private placement of 234,954,520 shares of Series B Convertible Preferred Stock (the “Series B Preferred Stock”). All 234,954,520 authorized shares of Series B Preferred Stock were designated at $0.29793 per share. As of December 31, 2017, 234,954,520 shares of the Series B Preferred Stock were issued and outstanding. These shares were issued in exchange for cash proceeds of $69.8 million, net of issuance costs. Dividends The holders of the Series A and Series B Preferred Stock are not entitled to receive dividends unless declared by the Board of Directors of the Company in accordance with the Company’s certificate of incorporation, as amended from time to time. No dividends have been declared since inception. Liquidation preference Upon a liquidation of the Company, the assets of the Company or proceeds available for distribution to the Company’s stockholders shall be paid as follows: (a) first, for each share of Series B Preferred Stock the greater of (i) one times the original purchase price plus declared and unpaid dividends on such share, or (ii) such amount as would have been payable had all shares of Series B Preferred Stock been converted to common stock immediately prior to such liquidation; and (b) then, for each share of Series A Preferred Stock the greater of (i) one times the original purchase price plus declared and unpaid dividends on such share, or (ii) such amount as would have been payable had all shares of (A) Series A‑1 Preferred Stock been converted to common stock, in the case of Series A‑1 Preferred Stock and (B) Series A‑2 Preferred Stock been converted to common stock, in the case of Series A‑2 Preferred Stock immediately prior to such liquidation. The balance of any proceeds shall be distributed pro rata to holders of common stock. If upon liquidation, the assets of the Company or proceeds available for distribution to its stockholders are insufficient to pay the holders of the Series B Preferred Stock as to their respective liquidation preferences the full amount entitled, the holders of the Series B Preferred Stock shall share ratably any distribution of the assets or proceeds available for distribution. If upon liquidation, the assets of the Company or proceeds available for distribution to its stockholders, after payment in full of the liquidation preferences to holders of the Series B Preferred Stock, are insufficient to pay the holders of the Series A Preferred Stock as to their respective liquidation preferences the full amount entitled, the holders of the Series A Preferred Stock shall share ratably any distribution of the remaining assets or proceeds available for distribution. Conversion update Shares of preferred stock are convertible into such number of fully paid and non‑assessable shares of common stock as determined by dividing the original issuance price by the conversion price at the time in effect, subject to adjustment. The original conversion price is $0.16472 for Series A‑1 Preferred Stock, $0.23061 for Series A‑2 Preferred Stock, and $0.29793 for Series B Preferred Stock, in each case, subject to adjustments to reflect the issuance of common stock, options, warrants, or other rights to subscribe for or to purchase common stock for a consideration per share, less than the conversion price then in effect and subsequent stock dividends, stock splits, combinations, or recapitalizations. Conversion is at the option of the respective holders of Series A and Series B Preferred Stock, although conversion is automatic upon the earlier of (a) the consummation of an underwritten public offering resulting in gross proceeds to the Company of at least $70 million and a share price of at least $0.446895 per share (subject to appropriate adjustment in the event of any stock dividend, stock split, combination or other similar recapitalization), or (b) the date and time, or the occurrence of an event, specified by the vote or written consent of the holders of at least majority of the then outstanding shares of Series A and Series B Preferred Stock, respectively; provided, that the outstanding shares of Series B Preferred Stock will not convert into shares of common stock pursuant to clause (b) without the approval of at least a majority of the then‑outstanding Series B Preferred Stock, including one or more holders of Series B Preferred Stock that (i) individually, or together with such holders’ affiliates, do not hold any Series A Preferred Stock and (ii) individually or collectively are the record holders of at least 30,208,439 shares of Series B Preferred Stock, subject to appropriate adjustment in the event of any stock dividend, stock split, combination or other similar recapitalization with respect to the Series B Preferred Stock. Voting rights Holders of the Series A and Series B Preferred Stock are entitled to vote as a single class with the holders of common stock and shall have one vote for each equivalent common share into which the preferred stock is convertible. The holders of Series B Preferred Stock are entitled to elect one director to the Board of Directors; the holders of Series A Preferred Stock are entitled to elect four directors to the Board of Directors; and the holders of Preferred Stock and the holders of common stock on an as‑converted to common stock basis, are entitled to elect the remaining directors. Tranche rights with Series A preferred stock The Company concluded that the Tranche Rights met the definition of a freestanding financial instrument, as the Tranche Rights were legally detachable and separately exercisable from the Series A‑1 Preferred Stock. Since the Series A Preferred Stock was contingently redeemable upon the occurrence of a deemed liquidation event, the Tranche Rights are classified as an asset or liability under ASC 480, Distinguishing Liabilities from Equity and are initially recorded at fair value. The Tranche Rights were measured at fair value at each reporting period. Since the Tranche Rights were subject to fair value accounting, the Company allocated the proceeds to the Tranche Rights based on the fair value at the date of issuance with the remaining proceeds being allocated to the Series A‑1 Preferred Stock. The estimated fair value of the Tranche Rights was determined using a Monte Carlo simulation. The simulation considered the timing of achieving the successful clinical milestone, the post‑money valuation as of May 2016, the risk‑free rate commensurate with the estimated time until the Series A‑2 transaction, and the volatility estimates. Based on the analysis, the Company recorded a preferred stock tranche liability of $2.1 million at the issue date to account for the obligation to issue shares of the Series A‑2 Preferred Stock at a predetermined fixed price at the future settlement date. At December 31, 2016, the Company remeasured the fair value of the Tranche Rights and recognized a non‑cash gain of $2.1 million which was included in other income in the statements of operations and comprehensive loss. The milestone event obligating the Company to issue the Series A‑2 Preferred Stock as of December 31, 2016 had been substantially achieved, and there was only a short amount of remaining time until the anticipated Series A‑2 transaction. The Company concluded that the estimated fair value of the Series A‑2 Preferred Stock was commensurate with the predetermined fixed price. As such, the preferred stock tranche liability had no value as of December 31, 2016. The milestone event occurred in January 2017, and the Company’s Board of Directors and the holders of at least a majority of the then‑outstanding Series A Preferred Stock certified that the milestone event had been achieved. The Series A‑2 Preferred Stock was issued on February 2, 2017. Common stock As of December 31, 2018 and 2017, the Company had reserved common stock, on an as if converted basis, for issuance as follows (in thousands): As of December 31, Series A-1 convertible preferred stock - 5,502 Series A-2 convertible preferred stock - 6,288 Series B convertible preferred stock - 8,517 Stock options issued and outstanding 3,959 1,498 Unvested restricted stock 195 488 4,154 22,293

Stock incentive plans

Stock incentive plans	12 Months Ended
	Dec. 31, 2018
Stock incentive plans
Stock incentive plans	11. Stock incentive plan In October 2015, the Company established a stock option plan (“2015 Plan”) to provide for the issuance of shares of common stock pursuant to stock options, stock appreciation rights, stock purchase rights, restricted stock agreements and long‑term performance awards granted to key employees, directors and consultants of the Company. The Company increased the number of shares reserved for issuance in the 2015 Plan in connection with each private placement of convertible preferred stock in May 2016, February 2017 and December 2017. On June 5, 2018, the Company’s stockholders approved the 2018 Stock Option and Incentive Plan (the “2018 Plan”), which became effective on June 20, 2018. The number of shares available for grant under the Company’s 2018 Plan as of December 31, 2018 was 3,816,895, which includes 505,046 shares of the Company’s common stock reserved under the Company’s 2015 Plan that became available for issuance upon the effectiveness of the 2018 Plan. No future issuance will be made under the 2015 Plan. The number of shares available for grant under the Company’s stock option plan were as follows (in thousands): Available for grant as of January 1, 2017 496 Plan amendment 3,145 Grants (1,226) Forfeitures and cancellations 4 Available for grant as of December 31, 2017 2,419 Plan amendment 3,899 Grants (2,515) Forfeitures and cancellations 14 Available for grant as of December 31, 2018 3,817 Stock‑based compensation expense Non‑cash stock‑based compensation expense recognized in the accompanying statements of operations and comprehensive loss relating to both stock options and restricted stock awards for the years ended December 31, 2018 and 2017 are as follows (in thousands): Year ended December 31, Research and development $ 866 $ 325 General and administrative 2,452 576 Total stock‑based compensation expense $ 3,318 $ 901 Restricted stock awards A summary of the status and changes of unvested restricted stock is presented below (in thousands, except per share amounts). Weighted‑ average grant date fair value Shares per share Outstanding as of January 1, 2017 781 $ 1.10 Granted — — Vested (293) $ 1.10 Repurchased — — Forfeited and canceled — — Outstanding as of December 31, 2017 488 $ 1.10 Granted — — Vested (293) $ 1.10 Repurchased — — Forfeited and canceled — — Outstanding as of December 31, 2018 195 $ 1.10 In 2015, the Company granted 1.5 million restricted stock awards with a weighted‑average grant date fair value per share of $1.10. The restricted stock awards generally vest over four years, or a change in the control of the Company, subject to continued employment with the Company. In the event of a change in control, the unvested restricted stock awards will be accelerated and fully vested immediately prior to the change in control. There are no performance‑based features or market conditions in the Company’s outstanding restricted stock awards. The fair value of restricted stock awards is determined based on the number of restricted stock awards granted and the fair value of the Company’s stock on the date of grant. Non-cash restricted stock award expense recognized in the accompanying statements of operations and comprehensive loss was $0.3 million for each of the years ended December 31, 2018 and 2017. The total fair value of shares that vested in 2018 was $0.3 million. At December 31, 2018, there was $0.2 million of unrecognized compensation cost related to unvested restricted stock awards that will be recognized as expense over a weighted-average period of 0.66 years. Stock options During the years ended December 31, 2018 and 2017, the Company granted 2.5 million and 1.2 million stock options, respectively. The options have a ten‑year life and generally vest over a period of four years, subject to continuous employment. Once the options are exercised, the shares are subject to transfer restrictions under the terms of the Company’s Stockholders’ Agreement. The weighted‑average grant date fair value per share of each option granted during the years ended December 31, 2018 and 2017 was $7.03 and $1.66, respectively. As of December 31, 2018, there was $16.4 million of total unrecognized stock‑based compensation expense related to non‑vested stock options which is expected to be recognized over a weighted‑average period of 2.96 years. The fair value of each option award is estimated on the date of grant using a Black‑Scholes option pricing valuation model that uses various assumptions regarding the: (1) expected volatility, (2) expected life of the option, (3) expected dividend yield, and (4) risk‑free interest rate. The Company uses the historical volatility of the share values of publicly traded companies within the biotech industry as a surrogate for the expected volatility of the Company’s common stock. A zero-dividend yield is also assumed in the stock option fair value computations. The expected life of the options represents the period of time that the options granted are expected to be outstanding and has been calculated utilizing the “simplified method” for awards that qualify as “plain vanilla” options. The risk‑free rate is based on the U.S. Treasury yield curve in effect at the time of grant of the award for time periods approximately equal to the expected term of the award. The specific assumptions used to determine the fair value of the stock options granted during the years ended December 31, 2018 and 2017 were as follows: Year ended December 31, Expected volatility Expected dividends None None Expected option life 6.08 Years 6.08 Years Risk-free rate 2.81 – 3.06% 2.02 – 2.40% The table below summarizes activity related to stock options (in thousands, except per share amounts): Weighted‑ Weighted‑ average average remaining Aggregate exercise contractual intrinsic Options Shares price term value Outstanding, January 1, 2017 276 $ 1.38 9.19 $ 89 Granted 1,226 2.48 Forfeited and canceled (4) 1.93 Outstanding, December 31, 2017 1,498 $ 2.48 8.93 $ 4,146 Granted 2,515 10.40 Exercised (40) 2.57 Forfeited and canceled (14) 4.79 Outstanding, December 31, 2018 3,959 $ 7.46 8.79 $ 35,984 Vested and expected to vest at December 31, 2018 3,959 $ 7.46 8.79 $ 35,984 Exercisable at December 31, 2018 881 $ 2.69 8.02 $ 12,205 Employee stock purchase plan On June 5, 2018, the Company's stockholders approved the 2018 Employee Stock Purchase Plan (the "ESPP"), which became effective upon the completion of the Company's initial public offering. A total of 314,697 shares of common stock were reserved for issuance under this plan. In addition, the number of shares of common stock that may be issued under the ESPP automatically increase on January 1 of each year through January 1, 2028, by the lesser of (i) 1% of the number of shares of the Company's common stock outstanding on the immediately preceding December 31 and (ii) such lesser number of shares as determined by the administrator of the Company's ESPP.

Net loss per share

Net loss per share	12 Months Ended
	Dec. 31, 2018
Net loss per share
Net loss per share	12. Net loss per share Basic and diluted net loss per share attributable to common stockholders was calculated as follows for the years ended December 31, 2018 and 2017 (in thousands, except per share data): Year ended December 31, Numerator: Net loss attributable to common stockholders $ (53,281) $ (32,068) Denominator: Weighted-average common shares outstanding—basic and diluted 20,199 5,196 Net loss per share attributable to common stockholders—basic and diluted $ (2.64) $ (6.17) The following common stock equivalents outstanding as of December 31, 2018 and 2017, were excluded from the computation of diluted net loss per share attributable to common stockholders for the periods presented because including them would have been anti-dilutive (in thousands): As of December 31, Series A-1 convertible preferred stock — 5,502 Series A-2 convertible preferred stock — 6,288 Series B convertible preferred stock — 8,517 Stock options issued and outstanding 3,959 1,498 Unvested restricted stock 195 488 4,154 22,293

Employee benefit plan

Employee benefit plan	12 Months Ended
	Dec. 31, 2018
Employee benefit plan
Employee benefit plan	13. Employee benefit plan Effective December 31, 2015, the Company established a defined contribution 401(k) plan (the “401(k) Plan”) for the benefit of its employees. All of the employees of the Company are eligible to participate in the 401(k) Plan which permits employees to make voluntary contributions up to the dollar limit allowed under the Internal Revenue Code. The 401(k) Plan also provides for matching contributions as defined by the Company of up to a combined total of 4% of an employee’s eligible annual compensation. The Company has recorded matching contributions of $0.3 million and $0.2 million for the years ended December 31, 2018 and 2017, respectively.

Income taxes

Income taxes	12 Months Ended
	Dec. 31, 2018
Income taxes
Income taxes	14. Income taxes Provision for income taxes There is no provision for income taxes because the Company has historically incurred operating losses and maintains a full valuation allowance against its net deferred tax assets. The reported amount of income tax expense for the years differs from the amount that would result from applying domestic federal statutory tax rates and pretax losses primarily because of changes in valuation allowance. Tax Cuts and Jobs Act With the enactment of the Tax Cuts and Jobs Act (“the Act”) on December 22, 2017, the Company’s 2017 financial results included a tax expense of $6.1 million from remeasuring federal net deferred tax assets from 34% to 21%, which was fully offset by a valuation allowance. As of December 31, 2018, the Company has completed its accounting for all tax effects related to the Act, and there were no material adjustments recorded during the year to the provisional amounts reflected in the Company’s 2017 financial statements. Deferred tax assets and valuation allowance Deferred tax assets reflect the tax effects of net operating losses (“NOLs”), tax credit carryovers, and temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. The most significant item of deferred tax assets is derived from the Company’s federal NOLs. At December 31, 2018, the Company had a U.S. federal NOL carryforward of $97.3 million which is available to offset future taxable income. Of the $97.3 million, $48.9 million will begin to expire in 2035 and the remaining $48.4 million has an indefinite carryforward period as a result of the Act. However, for NOLs arising after December 31, 2017, NOL carryforwards will be limited to 80% of taxable income. As of December 31, 2018, the Company had state NOL carryforwards of $9.2 million which have a 12-year carryforward period and will begin to expire starting in 2027. A reconciliation of the U.S statutory rate to the Company’s effective tax rate is as follows: Year ended December 31, Federal rate 21.0 % 34.0 % State rate 7.5 5.7 Effects of the Tax Cuts and Jobs Act — (18.9) Valuation allowance (26.8) (18.8) Provision to return (0.0) (2.6) Other (1.7) 0.6 -— % — % The significant components of the Company’s net deferred tax assets are as follows (in thousands): December 31, Deferred tax assets Net operating loss $ 27,749 $ 13,920 Accrued clinical trials 322 82 Accrued compensation 582 409 Accrued expenses and other, net 374 456 Total deferred tax assets 29,027 14,867 Less valuation allowance (28,963) (14,688) Net deferred tax assets 64 179 Deferred tax liabilities Stock‑based compensation and other, net (64) (179) Net deferred taxes $ — $ — Pursuant to Section 382 of the Internal Revenue Code, certain substantial changes in the Company’s ownership may result in a limitation on the amount of NOL carryforwards and tax carryforwards that may be used in future years. Utilization of the NOL and tax credit carryforwards may be subject to a substantial annual limitation under Section 382 of the Internal Revenue Code of 1986 (“IRC Section 382”) due to ownership change limitations that have occurred previously or that could occur in the future. These ownership changes may limit the amount of NOL and tax credit carryforwards that can be utilized annually to offset future taxable income and tax, respectively. During 2018, the Company performed a detailed analysis of their historical and current IRC Section 382 ownership changes that may limit the utilization of NOL carryforwards. Except for approximately $7.1 million of NOLs arising prior to the Company’s Series A preferred stock financing in May 2016, the entire remaining NOL carryforward is available for immediate use based on the IRC Section 382 analysis performed. There could also be additional ownership changes in the future which may result in limitations on the utilization of NOL carryforwards and credits. The Company files federal and state income tax returns and, in the normal course of business, the Company is subject to examination by these taxing authorities. As of December 31, 2018, the Company’s tax years through December 31, 2017 are subject to examination by the U.S. federal and state taxing authorities.

Commitments and contingencies

Commitments and contingencies	12 Months Ended
	Dec. 31, 2018
Commitments and contingencies
Commitments and contingencies	15. Commitments and contingencies From time to time, the Company is subject to occasional lawsuits, investigations and claims arising out of the normal conduct of business. The Company has no significant pending or threatened litigation as of December 31, 2018. In the normal course of business, the Company enters into contracts that contain a variety of indemnifications with its employees, licensors, suppliers and service providers. Further, the Company indemnifies its directors and officers who are, or were, serving at the Company’s request in such capacities. The Company’s maximum exposure under these arrangements is unknown at December 31, 2018. The Company does not anticipate recognizing any significant losses relating to these arrangements.

Subsequent events

Subsequent events	12 Months Ended
	Dec. 31, 2018
Subsequent events
Subsequent events	16. Subsequent events Grant of stock options under the 2018 Plan In January 2019, the Company granted options for the purchase of 1.0 million shares of common stock at a weighted-average exercise price of $19.33 per share.

Summary of significant accoun_2

Summary of significant accounting policies (Policies)	12 Months Ended
	Dec. 31, 2018
Summary of significant accounting policies
Use of estimates	Use of estimates The financial statements are prepared in conformity with GAAP. This process requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities as of the date of the financial statements and the reported amounts of expenses during the reporting period. Actual results could differ from those estimates.
Risk and uncertainties	Risk and uncertainties The Company’s future results of operations involve a number of risks and uncertainties. Factors that could affect the Company’s future operating results and cause actual results to vary materially from expectations include, but are not limited to, uncertainty of: future clinical study results, the scope, rate of progress and expense of the Company’s ongoing as well as any additional preclinical studies, clinical studies and other research and development activities, clinical study enrollment rate or design, the manufacturing of the Company’s product candidates, significant and changing government regulation, and the timing and receipt of any regulatory approvals. The Company’s product candidates require approvals from the U.S. Food and Drug Administration and comparable foreign regulatory agencies prior to commercial sales in their respective jurisdictions. There can be no assurance that any product candidates will receive the necessary approvals. If the Company was denied approval, approval was delayed or the Company was unable to maintain approval for any product candidate, it could have a materially adverse impact on the Company. The Company is dependent upon third‑party manufacturers to supply product for research and development activities in its programs. In particular, the Company relies and expects to continue to rely on a small number of manufacturers to supply it with its requirements for the active pharmaceutical ingredients and final drug product related to these programs. These programs could be adversely affected by a significant interruption in the supply of active pharmaceutical ingredients and final drug product.
Revenue recognition	Revenue recognition Revenue is recognized when all terms and conditions of the agreements have been met, including that persuasive evidence of an arrangement exists, delivery has occurred or services have been rendered, the price is fixed or determinable and collectability is reasonably assured. The Company is reimbursed for certain costs incurred on specified research projects under the terms and conditions of a Research Collaboration Agreement that are reported within collaboration and grant revenue (as discussed in Note 4) in the statements of operations and comprehensive loss. The amounts of the reimbursements are recorded as revenues on a gross basis in accordance with ASC 605‑45— Revenue Recognition—Principal Agent Consideration . The core principle is that the entity should recognize revenue to depict the transfer of goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. ASC 605‑45 specifies various indicators that support the reporting of revenue on a gross basis. As the Company is considered the primary obligor, is exposed to credit risk, and has discretion in changing and selecting the supplier, the Company recognizes these reimbursements on a gross basis. The related expenses are primarily recorded within research and development expenses in the statements of operations and comprehensive loss. The Company is also reimbursed for certain costs associated with government grants that provide funding for certain types of expenditures in connection with research and development activities over a contractually‑defined period. Revenue related to government grants is recognized in the period during which the related costs are incurred and the related services are rendered, provided that the applicable performance obligations under the government grants have been met. The revenue is reported on a gross basis within collaboration and grant revenue and the related expenses are recorded within both general and administrative expenses and research and development expenses in the statements of operations and comprehensive loss.
Accounts receivable	Accounts receivable Accounts receivable that management has the intent and ability to collect are reported in the balance sheets at outstanding amounts, less an allowance for doubtful accounts. During the years ended December 31, 2018 and 2017, one research collaborator, Allergan plc (“Allergan”) represented 75% and 80%, respectively, of the Company’s revenues (see Note 4). The associated accounts receivable were approximately $0.6 million and $0.6 million at December 31, 2018 and 2017, respectively. The remaining accounts receivable as of December 31, 2017 relate to the Company’s grants with the U.S. government. The Company writes off uncollectible receivables based on specific identification when the likelihood of collection is remote. No allowance was deemed necessary at December 31, 2018 and 2017.
Cash, cash equivalents and restricted cash	Cash, cash equivalents and restricted cash Cash and cash equivalents consist of cash and, if applicable, highly liquid investments with an original maturity of three months or less when purchased. The following table provides a reconciliation of cash, cash equivalents, and restricted cash reported within the balance sheets that sum to the total of the same such amounts shown in the statements of cash flows (amounts in thousands). As of December 31, Cash and cash equivalents $ 150,637 $ 92,136 Short-term and long-term restricted cash 491 473 Total cash, cash equivalents, and restricted cash shown in the statements of cash flows $ 151,128 $ 92,609 Amounts included in restricted cash represent those amounts required to be held as a security deposit in the form of letters of credit for the Company’s leased office facility and cash collateral held by credit card.
Concentrations of credit risk	Concentrations of credit risk The Company, at times, maintains cash and cash equivalents in accounts with a financial institution in excess of the amount insured by the Federal Deposit Insurance Corporation. The Company monitors the financial stability of this institution regularly and management does not believe there is significant credit risk associated with deposits in excess of federally insured amounts.
Fair value of financial instruments	Fair value of financial instruments ASC 820, Fair Value Measurement (“ASC 820”), establishes a fair value hierarchy for instruments measured at fair value that distinguishes between assumptions based on market data (observable inputs) and the Company’s own assumptions (unobservable inputs). Observable inputs are inputs that market participants would use in pricing the asset or liability based on market data obtained from sources independent of the Company. Unobservable inputs are inputs that reflect the Company’s assumptions about the inputs that market participants would use in pricing the asset or liability, and are developed based on the best information available in the circumstances. ASC 820 identifies fair value as the exchange price, or exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. As a basis for considering market participant assumptions in fair value measurements, ASC 820 establishes a three‑tier fair value hierarchy that distinguishes between the following: · Level 1 inputs are quoted prices (unadjusted) in active markets for identical assets or liabilities; · Level 2 inputs are inputs other than quoted prices included within Level 1 that are observable for the asset or liability, either directly or indirectly; and · Level 3 inputs are unobservable inputs that reflect the Company’s own assumptions about the assumptions market participants would use in pricing the asset or liability. Financial assets and liabilities are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. To the extent that the valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for instruments categorized in Level 3. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement. There were no Level 3 assets or liabilities as of December 31, 2018 or 2017. The carrying values reported in the Company’s balance sheets for cash and cash equivalents, restricted cash, accounts receivable, accounts payable, and accrued expenses are reasonable estimates of their fair values due to the short‑term nature of these items.
Property and equipment	Property and equipment Property and equipment are stated at cost. Maintenance and repairs are charged to expense as incurred. Additions, improvements and replacements are capitalized. Depreciation of property and equipment is provided for by the straight‑line method over the estimated useful lives of the related assets. The estimated useful lives of property and equipment are as follows: Description Estimated useful life Computer software and equipment 3 years Office equipment and furniture 5 years Laboratory equipment 5 years Leasehold improvements Lesser of the estimated useful life or term of the lease
Impairment of long-lived assets	Impairment of long‑lived assets Long‑lived assets consist of property and equipment. Long‑lived assets to be held and used are tested for recoverability whenever events or changes in business circumstances indicate that the carrying amount of the assets may not be fully recoverable. If the sum of the estimated future undiscounted cash flows expected to result from the use and eventual disposition of an asset is less than the carrying amount of the asset group, an impairment loss is recognized. Measurement of an impairment loss is based on the fair value of the asset group. The Company has not recorded any impairment losses on long‑lived assets for the years ended December 31, 2018 and 2017.
Research and development	Research and development Research and development expenses are comprised of costs incurred in performing research and development activities, including salaries and benefits, facilities costs, overhead costs, depreciation, contract services and other related costs. Research and development costs are expensed to operations as the related obligation is incurred. The Company has entered into various research and development contracts with research institutions, clinical research organizations, clinical manufacturing organizations and other companies. These agreements are generally cancelable, and related payments are recorded as research and development expenses as incurred. Payments for these activities are based on the terms of the individual agreements, which may differ from the pattern of costs incurred, and are reflected on the balance sheet as prepaid or accrued expenses. The Company records accruals for estimated ongoing research costs. When evaluating the adequacy of the accrued liabilities, the Company analyzes progress of the studies, including the phase or completion of events, invoices received and contracted costs. Significant judgments and estimates may be made in determining the accrued balances at the end of any reporting period. Actual results could differ from the Company’s estimates. The Company’s historical accrual estimates have not been materially different from the actual costs.
Convertible preferred stock	Convertible preferred stock The Company has applied the guidance in ASC 480‑10‑S99‑3A, SEC Staff Announcement: Classification and Measurement of Redeemable Securities and has therefore classified the Series A‑1, Series A‑2 and Series B convertible preferred stock (Note 10) as mezzanine equity. The convertible preferred stock is recorded outside of stockholders’ deficit because, in the event of certain deemed liquidation events considered not solely within the Company’s control, such as a merger, acquisition and sale of all or substantially all of the Company’s assets, the convertible preferred stock will become redeemable at the option of the holders. In the event of a change of control of the Company, proceeds received from the sale of such shares will be distributed in accordance with the liquidation preferences set forth in the Company’s Amended and Restated Certificate of Incorporation. The Company has determined not to adjust the carrying values of the convertible preferred stock to the liquidation preferences of such shares because of the uncertainty of whether or when such an event would occur. As described in Note 1, all previously outstanding convertible preferred stock was converted to common stock upon the completion of the Company’s IPO in June 2018.
Stock-based compensation	Stock‑based compensation The Company has stock‑based compensation plans that cover the Company’s directors and employees and are more fully described in Note 11. Stock‑based compensation cost is estimated at the grant date based on the fair value of the award, and the cost is recognized as expense ratably over the vesting period.
Income taxes	Income taxes The Company accounts for income taxes under the liability method in accordance with FASB ASC 740, Income Taxes. Under this method, deferred income tax assets and liabilities are determined based on differences between financial reporting and tax bases of assets and liabilities and are measured using the enacted tax rates and laws that will be in effect when the differences are expected to reverse. A valuation allowance is established if it is more likely than not that all, or some portion, of deferred income tax assets will not be realized. The Company has recorded a full valuation allowance to reduce its net deferred income tax assets to zero. In the event the Company were to determine that it would be able to realize some or all its deferred income tax assets in the future, an adjustment to the deferred income tax asset valuation allowance would increase income in the period such determination was made. The Company recognizes the effect of income tax positions only if those positions are more likely than not of being sustained upon an examination. Any recognized income tax positions would be measured at the largest amount that is greater than 50% likely of being realized. Changes in recognition or measurement would be reflected in the period in which the change in judgment occurs. At December 31, 2018 and 2017, the Company had no liability for income tax associated with uncertain tax positions. The Company would recognize any corresponding interest and penalties associated with its income tax positions in income tax expense. There was no income tax interest or penalties incurred in 2018 or 2017.
Segment data	Segment data The Company manages its operations as a single segment for the purposes of assessing performance and making operating decisions. The Company’s singular focus is on advancing therapies to treat disorders of the brain and nervous system. All tangible assets are held in the United States and all revenue is generated in the United States.
Comprehensive loss	Comprehensive loss Comprehensive loss is equal to net loss as presented in the accompanying statements of operations and comprehensive loss.
Net loss per share	Net loss per share Basic net loss per share is calculated by dividing the net loss by the weighted‑average number of shares of common stock outstanding during the period, without consideration for common stock equivalents. Diluted net loss per share is the same as basic net loss per share, since the effects of potentially dilutive securities are antidilutive given the Company has reported net losses for each period presented.

Summary of significant accoun_3

Summary of significant accounting policiess (Tables)	12 Months Ended
	Dec. 31, 2018
Summary of significant accounting policies
Schedule of cash, cash equivalents and restricted cash	The following table provides a reconciliation of cash, cash equivalents, and restricted cash reported within the balance sheets that sum to the total of the same such amounts shown in the statements of cash flows (amounts in thousands). As of December 31, Cash and cash equivalents $ 150,637 $ 92,136 Short-term and long-term restricted cash 491 473 Total cash, cash equivalents, and restricted cash shown in the statements of cash flows $ 151,128 $ 92,609
Schedule of estimated useful lives of assets	Description Estimated useful life Computer software and equipment 3 years Office equipment and furniture 5 years Laboratory equipment 5 years Leasehold improvements Lesser of the estimated useful life or term of the lease

Fair value measurements (Tables

Fair value measurements (Tables)	12 Months Ended
	Dec. 31, 2018
Fair value measurements
Schedule of assets measured at fair value	Assets measured at fair value as of December 31, 2018 are as follows (in thousands): December 31, Level 1 Level 2 Level 3 Assets Money market funds, included in cash and cash equivalents $ 150,151 $ 150,151 $ — $ — Money market funds, included in restricted cash $ 252 $ 252 — — Money market funds, included in other assets 239 239 — — $ 150,642 $ 150,642 $ — $ — Assets measured at fair value as of December 31, 2017 are as follows (in thousands): December 31, Level 1 Level 2 Level 3 Assets Money market funds, included in cash and cash equivalents $ 89,553 $ 89,553 $ — $ — Money market funds, included in other assets 317 317 — — $ 89,870 $ 89,870 $ — $ —

Prepaid expenses and other cu_2

Prepaid expenses and other current assets (Tables)	12 Months Ended
	Dec. 31, 2018
Prepaid expenses and other current assets
Schedule of prepaid expenses and other current assets	Prepaid expenses and other current assets consist of the following (in thousands): As of December 31, Prepaid clinical $ 728 $ 1,718 Prepaid insurance 673 137 Other prepaid expenses and current assets 383 105 Total prepaid expenses and other current assets $ 1,784 $ 1,960

Property and equipment (Tables)

Property and equipment (Tables)	12 Months Ended
	Dec. 31, 2018
Property and equipment
Schedule of property and equipment	Property and equipment are as follows (in thousands): As of December 31, Computer software and equipment $ 15 $ 15 Office equipment and furniture 176 92 Laboratory equipment 1,571 1,529 Leasehold improvements 1,051 748 Construction in progress — 22 Less accumulated depreciation (1,123) (590) Property and equipment, net $ 1,690 $ 1,816

Accrued expenses and other cu_2

Accrued expenses and other current liabilities (Tables)	12 Months Ended
	Dec. 31, 2018
Accrued expenses and other current liabilities
Schedule of accrued expenses and other current liabilities	Accrued expenses and other current liabilities consist of the following (in thousands): As of December 31, Employee-related expenses $ 2,043 $ 1,435 Development costs and sponsored research 915 737 Clinical trials 607 69 Other 431 594 Total accrued expenses and other current liabilities $ 3,996 $ 2,835

Operating leases (Tables)

Operating leases (Tables)	12 Months Ended
	Dec. 31, 2018
Operating leases
Schedule of aggregate future minimum annual rental commitments under non-cancelable lease agreements	Aggregate future minimum annual rental commitments under these non‑cancelable lease agreements are as follows at December 31, 2018 (in thousands): Year ending December 31, 2019 $ 848 2020 860 2021 871 2022 587 2023 — Thereafter — $ 3,166

Convertible preferred stock, _2

Convertible preferred stock, tranche liability and stockholders’ equity (deficit) (Tables)	12 Months Ended
	Dec. 31, 2018
Convertible preferred stock, tranche liability and stockholders’ deficit
Summary of convertible preferred stock	At December 31, 2017, convertible preferred stock consisted of the following (in thousands, except per share amounts): Shares Issuance Shares issued and price per Carrying Liquidation authorized outstanding share value preference Series A‑1 151,773 151,773 0.16472 $ 22,650 $ 25,000 Series A‑2 173,453 173,453 0.23061 39,979 40,000 Series B 234,955 234,955 0.29793 69,757 70,000 Total 560,181 560,181 $ 132,386 $ 135,000
Schedule of the Company's common stock reserved for issuance, on an as if converted basis,	As of December 31, 2018 and 2017, the Company had reserved common stock, on an as if converted basis, for issuance as follows (in thousands): As of December 31, Series A-1 convertible preferred stock - 5,502 Series A-2 convertible preferred stock - 6,288 Series B convertible preferred stock - 8,517 Stock options issued and outstanding 3,959 1,498 Unvested restricted stock 195 488 4,154 22,293

Stock incentive plans (Tables)

Stock incentive plans (Tables)	12 Months Ended
	Dec. 31, 2018
Stock incentive plans
Schedule of available shares for grant under the Company’s stock option plan	The number of shares available for grant under the Company’s stock option plan were as follows (in thousands): Available for grant as of January 1, 2017 496 Plan amendment 3,145 Grants (1,226) Forfeitures and cancellations 4 Available for grant as of December 31, 2017 2,419 Plan amendment 3,899 Grants (2,515) Forfeitures and cancellations 14 Available for grant as of December 31, 2018 3,817
Allocation of stock-based compensation expenses	Non‑cash stock‑based compensation expense recognized in the accompanying statements of operations and comprehensive loss relating to both stock options and restricted stock awards for the years ended December 31, 2018 and 2017 are as follows (in thousands): Year ended December 31, Research and development $ 866 $ 325 General and administrative 2,452 576 Total stock‑based compensation expense $ 3,318 $ 901
Summary of status and changes of unvested restricted stock	A summary of the status and changes of unvested restricted stock is presented below (in thousands, except per share amounts). Weighted‑ average grant date fair value Shares per share Outstanding as of January 1, 2017 781 $ 1.10 Granted — — Vested (293) $ 1.10 Repurchased — — Forfeited and canceled — — Outstanding as of December 31, 2017 488 $ 1.10 Granted — — Vested (293) $ 1.10 Repurchased — — Forfeited and canceled — — Outstanding as of December 31, 2018 195 $ 1.10
Schedule of assumptions used to determine the fair value of the stock options granted	Year ended December 31, Expected volatility Expected dividends None None Expected option life 6.08 Years 6.08 Years Risk-free rate 2.81 – 3.06% 2.02 – 2.40%
Summary of stock option activity	The table below summarizes activity related to stock options (in thousands, except per share amounts): Weighted‑ Weighted‑ average average remaining Aggregate exercise contractual intrinsic Options Shares price term value Outstanding, January 1, 2017 276 $ 1.38 9.19 $ 89 Granted 1,226 2.48 Forfeited and canceled (4) 1.93 Outstanding, December 31, 2017 1,498 $ 2.48 8.93 $ 4,146 Granted 2,515 10.40 Exercised (40) 2.57 Forfeited and canceled (14) 4.79 Outstanding, December 31, 2018 3,959 $ 7.46 8.79 $ 35,984 Vested and expected to vest at December 31, 2018 3,959 $ 7.46 8.79 $ 35,984 Exercisable at December 31, 2018 881 $ 2.69 8.02 $ 12,205

Net loss per share (Tables)

Net loss per share (Tables)	12 Months Ended
	Dec. 31, 2018
Net loss per share
Schedule of basic and diluted net loss per share attributable to common stockholders calculation	Basic and diluted net loss per share attributable to common stockholders was calculated as follows for the years ended December 31, 2018 and 2017 (in thousands, except per share data): Year ended December 31, Numerator: Net loss attributable to common stockholders $ (53,281) $ (32,068) Denominator: Weighted-average common shares outstanding—basic and diluted 20,199 5,196 Net loss per share attributable to common stockholders—basic and diluted $ (2.64) $ (6.17)
Schedule of anti-dilutive securities excluded from computation of diluted net loss per share	The following common stock equivalents outstanding as of December 31, 2018 and 2017, were excluded from the computation of diluted net loss per share attributable to common stockholders for the periods presented because including them would have been anti-dilutive (in thousands): As of December 31, Series A-1 convertible preferred stock — 5,502 Series A-2 convertible preferred stock — 6,288 Series B convertible preferred stock — 8,517 Stock options issued and outstanding 3,959 1,498 Unvested restricted stock 195 488 4,154 22,293

Income taxes (Tables)

Income taxes (Tables)	12 Months Ended
	Dec. 31, 2018
Income taxes
Summary of reconciliation of U.S. statutory rate to the Company’s effective tax rate	Year ended December 31, Federal rate 21.0 % 34.0 % State rate 7.5 5.7 Effects of the Tax Cuts and Jobs Act — (18.9) Valuation allowance (26.8) (18.8) Provision to return (0.0) (2.6) Other (1.7) 0.6 -— % — %
Schedule of significant components of the Company’s net deferred tax assets	The significant components of the Company’s net deferred tax assets are as follows (in thousands): December 31, Deferred tax assets Net operating loss $ 27,749 $ 13,920 Accrued clinical trials 322 82 Accrued compensation 582 409 Accrued expenses and other, net 374 456 Total deferred tax assets 29,027 14,867 Less valuation allowance (28,963) (14,688) Net deferred tax assets 64 179 Deferred tax liabilities Stock‑based compensation and other, net (64) (179) Net deferred taxes $ — $ —

Organization (Details)

Organization (Details) $ / shares in Units, $ in Thousands	Jun. 25, 2018USD ($)$ / sharesshares	Jun. 07, 2018	Dec. 31, 2018USD ($)$ / sharesshares	Dec. 31, 2017USD ($)$ / sharesshares
Organization
Accumulated deficit | $			$ (105,538)	$ (52,257)
Payment of offering costs | $			$ 3,012
Reverse stock split ratio		0.0004
Preferred stock, shares authorized			10,000,000	0
Preferred stock, par value (in dollars per share) | $ / shares			$ 0.01	$ 0.01
Preferred stock, shares issued			0	0
Preferred stock, shares outstanding			0	0
Cash and cash equivalents | $			$ 150,637	$ 92,136
IPO
Organization
Common stock issued and sold in initial public offering	7,359,998
Public offering price of the shares sold | $ / shares	$ 16
Net proceeds from issuance of common stock | $	$ 106,500
Payment of offering costs | $	$ 3,000
Number of preferred stock converted into common stock	20,306,497
Underwriters' option
Organization
Common stock issued and sold in initial public offering	959,999

Summary of significant accoun_4

Summary of significant accounting policies (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018USD ($)customer	Dec. 31, 2017USD ($)customer
Concentration Risk [Line Items]
Accounts receivable	$ 578	$ 937
Allowance for accounts receivable	0	0
Allergan
Concentration Risk [Line Items]
Accounts receivable	$ 600	$ 600
Customer Concentration Risk | Revenue | Allergan
Concentration Risk [Line Items]
Number of customers | customer	1	1
Concentration risk percentage	75.00%	80.00%

Summary of significant accoun_5

Summary of significant accounting policies - Cash, cash equivalents, and restricted cash (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Summary of significant accounting policies
Cash and cash equivalents	$ 150,637	$ 92,136
Short term and long term restricted cash	491	473
Total cash, cash equivalents, and restricted cash shown in the statements of cash flows	$ 151,128	$ 92,609	$ 16,953

Summary of significant accoun_6

Summary of significant accounting policies - Property and equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Assets measured at fair value	$ 150,642	$ 89,870
Impairment of long lived assets	$ 0	0
Computer software and equipment
Property, Plant and Equipment [Line Items]
Estimated useful life	3 years
Office equipment and furniture
Property, Plant and Equipment [Line Items]
Estimated useful life	5 years
Laboratory equipment
Property, Plant and Equipment [Line Items]
Estimated useful life	5 years
Level 3
Property, Plant and Equipment [Line Items]
Assets measured at fair value	$ 0	0
Liabilities measured at fair value	$ 0	$ 0

Summary of significant accoun_7

Summary of significant accounting policies - Income taxes (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Summary of significant accounting policies
Deferred Tax Assets, Net	$ 0
Uncertain tax positions	0	$ 0
Interest or penalties recorded	$ 0	$ 0

Research collaboration agreem_2

Research collaboration agreement with Allergan (Details) $ in Thousands	Jul. 24, 2015USD ($)Option	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)
Research collaboration and development services agreements with Allergan
Collaboration and grant revenue		$ 6,574	$ 4,962
Research and development		48,788	31,644
RCA
Research collaboration and development services agreements with Allergan
Amount to be received for each option exercised	$ 1,000
Number of options to acquire molecules | Option	3
Collaboration and grant revenue		1,000
Research and development		$ 7,900	$ 7,900
Development activities reimbursement percentage		50.00%	50.00%
Development activities expenses reimbursed		$ 3,900	$ 3,900

Fair value measurements (Detail

Fair value measurements (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Fair value measurements
Assets measured at fair value	$ 150,642	$ 89,870
Money market funds, included in cash and cash equivalents
Fair value measurements
Money market funds	150,151	89,553
Money market funds, included in restricted cash
Fair value measurements
Money market funds	252
Money market funds, included in other assets
Fair value measurements
Money market funds	239	317
Level 1
Fair value measurements
Assets measured at fair value	150,642	89,870
Level 1 | Money market funds, included in cash and cash equivalents
Fair value measurements
Money market funds	150,151	89,553
Level 1 | Money market funds, included in restricted cash
Fair value measurements
Money market funds	252
Level 1 | Money market funds, included in other assets
Fair value measurements
Money market funds	239	317
Level 3
Fair value measurements
Assets measured at fair value	$ 0	$ 0

Prepaid expenses and other cu_3

Prepaid expenses and other current assets (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Prepaid expenses and other current assets
Prepaid clinical	$ 728	$ 1,718
Prepaid insurance	673	137
Other prepaid expenses and current assets	383	105
Total prepaid expenses and other current assets	$ 1,784	$ 1,960

Property and equipment (Details

Property and equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Property and equipment
Less accumulated depreciation	$ (1,123)	$ (590)
Property and equipment, net	1,690	1,816
Depreciation and amortization	457	405
Computer software and equipment
Property and equipment
Property and equipment, gross	15	15
Office equipment and furniture
Property and equipment
Property and equipment, gross	176	92
Laboratory equipment
Property and equipment
Property and equipment, gross	1,571	1,529
Leasehold improvements
Property and equipment
Property and equipment, gross	$ 1,051	748
Construction in progress
Property and equipment
Property and equipment, gross		$ 22

Accrued expenses and other cu_3

Accrued expenses and other current liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Accrued expenses and other current liabilities
Employee-related expenses	$ 2,043	$ 1,435
Development costs and sponsored research	915	737
Clinical trials	607	69
Other	431	594
Total accrued expenses and other current liabilities	$ 3,996	$ 2,835

Operating leases (Details)

Operating leases (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Jul. 18, 2018ft²	Oct. 13, 2016USD ($)ft²item
Operating leases
Leased space (in square feet) | ft²			6,172	16,500
Lease renewal options | item				1
Renewal term (in years)				5 years
Deferred lease incentive				$ 400
Security deposit in the form of letter of credit	$ 400	$ 400
Rent expense inclusive of lease incentives	700	$ 600
Estimated sublease base rent	800
Future minimum annual rental commitments
2019	848
2020	860
2021	871
2022	587
Total	$ 3,166

Convertible preferred stock, _3

Convertible preferred stock, tranche liability and stockholders’ equity (deficit) - Convertible preferred stock (Details) - USD ($) $ / shares in Units, $ in Thousands	Dec. 11, 2017	May 04, 2016	Dec. 31, 2017	Dec. 31, 2018
Temporary Equity [Line Items]
Shares authorized			560,181,000
Shares issued			560,181,000
Shares outstanding			560,181,000
Carrying value			$ 132,386
Liquidation preference			135,000
Series A Preferred Stock
Temporary Equity [Line Items]
Cash proceeds, net of issuance cost			$ 64,700
Series A Preferred Stock | Private placement
Temporary Equity [Line Items]
Shares authorized		325,225,719
Series A‑1
Temporary Equity [Line Items]
Shares authorized			151,773,000
Shares issued			151,772,701
Shares outstanding			151,772,701
Issuance price per share			$ 0.16472
Carrying value			$ 22,650
Liquidation preference			$ 25,000
Series A‑1 | Private placement
Temporary Equity [Line Items]
Shares authorized		151,772,701
Issuance price per share		$ 0.16472
Series A‑1 | Private placement | Maximum
Temporary Equity [Line Items]
New shares issued under the agreement		151,772,701
Series A‑2
Temporary Equity [Line Items]
Shares authorized			173,453,000
Shares issued			173,453,018
Shares outstanding			173,453,018
Issuance price per share			$ 0.23061	$ 0.23061
Carrying value			$ 39,979
Liquidation preference			$ 40,000
Series A‑2 | Private placement
Temporary Equity [Line Items]
Shares authorized		173,453,018
Issuance price per share		$ 0.23061
New shares issued under the agreement		173,453,018
Series B preferred stock
Temporary Equity [Line Items]
Shares authorized			234,955,000
Shares issued			234,954,520
Shares outstanding			234,955,000
Issuance price per share			$ 0.29793
Carrying value			$ 69,757
Liquidation preference			70,000
Cash proceeds, net of issuance cost			$ 69,800
Series B preferred stock | Private placement
Temporary Equity [Line Items]
Issuance price per share	$ 0.29793
New shares issued under the agreement	234,954,520

Convertible preferred stock, _4

Convertible preferred stock, tranche liability and stockholders’ equity (deficit) - Conversion update, Voting rights and Tranche rights (Details) $ / shares in Units, $ in Millions	Dec. 11, 2017USD ($)Vote$ / sharesshares	May 04, 2016USD ($)Vote$ / shares	Dec. 31, 2016USD ($)
Threshold gross proceeds for automatic converstion | $	$ 70
Threshold share price for automatic converstion | $ / shares	$ 0.446895
Gain from changes in the fair value of Preferred Stock Tranche Liability | $			$ 2.1
Series A Preferred Stock
Number of votes per share | Vote		1
Number of director entitled to be elected by preferred shareholders | Vote		4
Series A‑1
Conversion price | $ / shares		$ 0.16472
Series A‑2
Conversion price | $ / shares		$ 0.23061
Preferred stock tranche liability | $		$ 2.1
Series B preferred stock
Conversion price | $ / shares	$ 0.29793
Approval of threshold shares | shares	30,208,439
Number of votes per share | Vote	1
Number of director entitled to be elected by preferred shareholders | Vote	1

Convertible preferred stock, _5

Convertible preferred stock, tranche liability and stockholders’ equity (deficit) - Common stock (Details) - shares shares in Thousands	Dec. 31, 2018	Dec. 31, 2017
Common stock reserved for issuance	4,154	22,293
Stock options
Common stock reserved for issuance	3,959	1,498
Restricted stock awards
Common stock reserved for issuance	195	488
Series A‑1
Common stock reserved for issuance		5,502
Series A‑2
Common stock reserved for issuance		6,288
Series B preferred stock
Common stock reserved for issuance		8,517

Stock incentive plans (Details)

Stock incentive plans (Details) - shares	Dec. 31, 2018	Sep. 30, 2018
2018 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards available for future grant	3,816,895
2015 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards available for future grant		505,046

Stock incentive plans - Shares

Stock incentive plans - Shares available for grant (Details) - Stock options - shares shares in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Available for grant Beginning of the period	2,419	496
Plan amendment	3,899	3,145
Grants	(2,515)	(1,226)
Exercised	(40)
Forfeitures and cancellations	14	4
Available for grant End of the period	3,817	2,419

Stock incentive plans - Stock b

Stock incentive plans - Stock based compensation expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 3,318	$ 901
Research and development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	866	325
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 2,452	$ 576

Stock incentive plans - Restric

Stock incentive plans - Restricted stock awards (Details) - USD ($) $ / shares in Units, shares in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2015
Weighted‑average grant date fair value per share
Stock-based compensation expense	$ 3,318,000	$ 901,000
Restricted stock awards
Shares
Outstanding, at the beginning of the period	488	781
Granted			1,500
Vested	(293)	(293)
Outstanding, at the end of the period	195	488
Weighted‑average grant date fair value per share
Outstanding, at the beginning of the period	$ 1.10	$ 1.10
Granted			$ 1.10
Vested	1.10	1.10
Outstanding, at the end of the period	$ 1.10	$ 1.10
Vesting period	4 years
Stock-based compensation expense	$ 300,000	$ 300,000
Fair value of shares vested	300,000
Compensation expenses not yet recognized	$ 0.2
Term in which unrecognized compensation expenses will be recognized	7 months 28 days

Stock incentive plans - Fair va

Stock incentive plans - Fair value assumptions (Details) - Stock options	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility	75.00%	75.00%
Expected dividends	0.00%	0.00%
Expected option life	6 years 29 days	6 years 29 days
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free rate	2.81%	2.02%
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free rate	3.06%	2.40%

Stock incentive plans - Activit

Stock incentive plans - Activity related to stock options (Details) - Stock options - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Shares
Outstanding, at the beginning of the period	1,498	276
Granted	2,515	1,226
Exercised	(40)
Forfeited and canceled	(14)	(4)
Outstanding, at the end of the period	3,959	1,498	276
Vested and expected to vest	3,959
Exercisable	881
Weighted-average exercise price
Outstanding, at the beginning of the period	$ 2.48	$ 1.38
Granted	10.40	2.48
Exercised	2.57
Forfeited and canceled	4.79	1.93
Outstanding, at the end of the period	7.46	$ 2.48	$ 1.38
Vested and expected to vest	7.46
Exercisable at the end of the period	$ 2.69
Weighted-average remaining contractual term
Weighted-average remaining contractual term	8 years 9 months 15 days	8 years 11 months 5 days	9 years 2 months 9 days
Vested and expected to vest	8 years 9 months 15 days
Exercisable	8 years 7 days
Aggregate intrinsic value
Outstanding, at the beginning of the period	$ 4,146	$ 89
Outstanding, at the end of the period	35,984	$ 4,146	$ 89
Vested and expected to vest	35,984
Exercisable	$ 12,205
Term of award	10 years
Vesting period	4 years
Weighted-average grant date fair value per share	$ 7.03	$ 1.66
Unrecognized stock-based compensation related to non-vested stock options	$ 16,400
Term in which unrecognized compensation expenses will be recognized		2 years 11 months 16 days

Stock incentive plans - Employe

Stock incentive plans - Employee Stock Purchase Plan (Details) - shares	Jun. 05, 2018	Dec. 31, 2018	Dec. 31, 2017
Subsidiary, Sale of Stock [Line Items]
Common stock reserved for issuance		4,154,000	22,293,000
Employee Stock Purchase Plan
Subsidiary, Sale of Stock [Line Items]
Common stock reserved for issuance	314,697
Maximum percentage increase in shares available for issuance under the ESPP	1.00%

Net loss per share (Details)

Net loss per share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Numerator:
Net loss attributable to common stockholders	$ (53,281)	$ (32,068)
Denominator:
Weighted-average common shares outstanding—basic and diluted	20,199	5,196
Net loss per share attributable to common stockholders—basic and diluted	$ (2.64)	$ (6.17)

Net loss per share - Anti-dilut

Net loss per share - Anti-dilutive securities (Details) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Common stock equivalents outstanding excluded from the computation of diluted net loss per share attributable to common stockholders
Outstanding anti-dilutive securities excluded from computation of diluted net loss per share	4,154	22,293
Series A-1 convertible preferred stock
Common stock equivalents outstanding excluded from the computation of diluted net loss per share attributable to common stockholders
Outstanding anti-dilutive securities excluded from computation of diluted net loss per share		5,502
Series A-2 convertible preferred stock
Common stock equivalents outstanding excluded from the computation of diluted net loss per share attributable to common stockholders
Outstanding anti-dilutive securities excluded from computation of diluted net loss per share		6,288
Series B preferred stock
Common stock equivalents outstanding excluded from the computation of diluted net loss per share attributable to common stockholders
Outstanding anti-dilutive securities excluded from computation of diluted net loss per share		8,517
Stock options
Common stock equivalents outstanding excluded from the computation of diluted net loss per share attributable to common stockholders
Outstanding anti-dilutive securities excluded from computation of diluted net loss per share	3,959	1,498
Unvested restricted stock
Common stock equivalents outstanding excluded from the computation of diluted net loss per share attributable to common stockholders
Outstanding anti-dilutive securities excluded from computation of diluted net loss per share	195	488

Employee benefit plan (Details)

Employee benefit plan (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Employee benefit plan
Matching contribution as a percentage	4.00%
Matching contribution	$ 0.3	$ 0.2

Income taxes (Details)

Income taxes (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Income taxes
Income taxes	$ 0
Provisional net tax expense	$ 6.1
Federal effective tax rate	21.00%	34.00%

Income taxes - Deferred tax ass

Income taxes - Deferred tax assets and valuation allowance (Details) $ in Millions	12 Months Ended
	Dec. 31, 2018USD ($)
Federal
Operating Loss Carryforwards [Line Items]
Net operating losses	$ 97.3
Net operating loss carryforwards that expire	48.9
Net operating losses that never expire	$ 48.4
Net operating loss carryforward taxable income limit percentage	80.00%
State
Operating Loss Carryforwards [Line Items]
NOL carryforward period	12 years
Net operating loss carryforwards that expire	$ 9.2

Income taxes - Reconciliation (

Income taxes - Reconciliation (Details)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Income taxes
Federal rate	21.00%	34.00%
State rate	7.50%	5.70%
Effects of the Tax Cuts and Jobs Act		(18.90%)
Valuation allowance	(26.80%)	(18.80%)
Provision to return	0.00%	(2.60%)
Other	(1.70%)	0.60%

Income taxes - Components of ne

Income taxes - Components of net deferred tax assets (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Deferred tax assets
Net operating loss	$ 27,749	$ 13,920
Accrued clinical trials	322	82
Accrued compensation	582	409
Accrued expenses and other, net	374	456
Total deferred tax assets	29,027	14,867
Less valuation allowance	(28,963)	(14,688)
Net deferred tax assets	64	179
Deferred tax liabilities
Stock-based compensation and other, net	(64)	$ (179)
Net deferred taxes	0
Net operating loss carryforwards with no taxable income limitation	$ 7,100

Subsequent events (Details)

Subsequent events (Details) - Subsequent Event - 2018 Plan shares in Millions	1 Months Ended
	Jan. 31, 2019$ / sharesshares
Subsequent Event [Line Items]
Granted | shares	1
weighted average exercise price | $ / shares	$ 19.33